Ireland Red List No. 2 : Non-marine molluscs

Based on almost 80,000 records for Ireland, 150 native species of non-marine mollusc are evaluated for
their conservation status using International Union for the Conservation of Nature (IUCN) criteria
(IUCN, 2001, 2003). Two are considered to be regionally extinct, five critically endangered, fourteen
endangered, twenty-six vulnerable, six near threatened, and the rest of least concern, or data deficient.
Ireland’s non-marine molluscan fauna is of international importance. Ten species have populations of
significant international worth, having large proportions of their global population in Ireland.
Ashfordia granulata and Leisotyla anglica are two examples of such species; both are near endemics to
Britain and Ireland, with Ireland having at least a fifth of their global populations. Seven species have
been listed on the global IUCN red list, for example Myxas glutinosa and Quickella arenaria, both of
which are endangered species in Ireland. Six species are legally protected under European legislation.
Of these legally protected species, only the Kerry slug, Geomalacus maculosus, is not considered
threatened in Ireland. However, the Irish population of this species is of particular international
importance as the species is restricted to south-west Ireland and northern Iberia, and the Iberian
populations are severely threatened.
Some species are rare in Ireland as they are at the edge of their range or climatic tolerances (e.g.
Pomatias elegans). For species that are declining in Ireland there are multiple drivers of population loss.
Species declines are primarily driven by habitat loss (e.g. loss of marginal agricultural wetlands
through drainage impacting species such as Vertigo antivertigo), habitat change (e.g. reduced water
quality impacting species such as Pisidium pseudosphaerium and Margaritifera margaritifera) and habitat
management (e.g. woodland management practices impacting species such as Spermodea lamellata). To
a lesser extent species may be declining due to climate change (e.g. Pisidium conventus, a cold, deep
water, montane species) and the impact of invasive species (Anodonta cygnea and A. anatina, the swan
and duck mussels, are being severely impacted by the invasive species Dreissena polymorpha, the zebra
mussel).
The importance of water quality and the reduction of habitat loss and change across a spectrum of
habitats are identified as important components in conserving the non-marine molluscan fauna on the
island of Ireland.

The National Parks and Wildlife Service Red Lists are available online at http://www.npws.ie/publications/redlists/